1. Field of the Invention
The invention relates to a motor vehicle in which a microphone or a microphone array for a hands-free voice communications system is fitted in a passenger cell. Such hands-free voice communications systems have for some time been the subject of great interest, because their use is statutorily prescribed for the use of a telephone in a moving motor vehicle. The applicability of such a hands-free microphone is not limited to mobile telephony, however. For example, voice signals picked up by the microphone can also be relayed to another part of the vehicle via loudspeakers or may be used by a voice recognition system in order to identify commands spoken into the microphone and to have these commands executed by other vehicle systems.
2. Description of Related Art
A favorable location of the microphone is essential for good-quality registering of the voice. Although fitting it in front of the driver's face would be acoustically advantageous, this has to be ruled out since it obstructs the driver's vision. With a microphone fitted at dashboard height there is the risk that it will sometimes be masked, in particular by the driver's arm movements when steering. Fitting the microphone above head height, to the headliner of the passenger cell, is described, for example, in DE 10203599 A1, JP 2001105989 AH and US 2002/0031234 A1, which discloses a motor vehicle in this field. In particular, US 2002/0031234 gives consideration to the location of a microphone on a console centrally placed on the headliner or on a rear-view mirror fitted to the windshield. Such a location, laterally offset in relation to the normal line of vision and speaking direction of the driver is, however, not ideal from the acoustic standpoint, so that it is proposed, through the use of a microphone array, to arrive at a sensitivity characteristic adjusted to the driver, in order to be able to register his voice with a high level of quality. However, the use of multiple microphones and the in-phase superimposition of the signals delivered by these in order to achieve a directional characteristic make such hands-free voice communications systems costly and expensive.